1. Field of the Invention
The present invention relates to a surface cleaning apparatus and more particularly to an air sweeping apparatus.
2. Description of the Prior Art
Recirculating air systems have been in use for many years and are preferred over vacuum based systems for sweeping large areas. They generally comprise an air stream that is constrained to move along an air circulation loop. The air stream is pressurized, directed onto a surface to entrain debris, drawn by low pressure into a suitable receptacle, filtered and then re-pressurized. In some recirculating air systems some of the air is diverted from the loop and discharged to the atmosphere. These machines may also include brooms to assist in debris removal.
There are at least three types of head assemblies commonly used on recirculating air sweepers. The first type uses a broom or brooms to mechanically sweep debris into a row where it is then drawn up by a relatively small, lower pressure suction head. The second type of head assembly is a cross flow head. This is typically a single chambered head which extends transversely to the direction of motion of the head as it moves along a surface being swept. With this head, air is blown into one end of the head, travels along the length thereof and is then drawn out the other end. The third type of head assembly is a two-chambered head. Here, air fills a first pressure chamber that is above or behind a second pick-up or sweeping chamber. Pressurized air from the first chamber is fed into a gap or nozzle that extends along the sweeping chamber of the head. As the pressurized air exits the gap, it is formed into an air curtain or sheet which is directed towards the surface being swept in a direction substantially coincident with the direction of travel. The pressurized air entrains debris in high velocity turbulent air flow and transports the debris along the sweeping chamber of the head assembly until it is drawn out of the head to a suitable receptacle by low pressure. Once the air stream/debris mixture leaves the head, it is conveyed into a hopper where the debris is separated out of the air stream and collected for later disposal. The air then continues out of the hopper to be re-pressurized after which a majority of the air stream is directed back into the head assembly and the remainder is exhausted to the atmosphere. One example of a sweeper for road or other surfaces is disclosed in U.S. Pat. No. 4,660,248, the sweeper including a pickup head, a hopper into which debris is adapted to be discharged, and a centrifugal separator for filtering the air stream. Other aspects of recirculating air sweepers are disclosed in U.S. Pat. Nos. 4,006,511, and 4,109,341.
The aforementioned recirculating air systems have their drawbacks. One drawback is that as the air stream moves along the sweeping chamber of the head and exits the head, the air stream must make a series of sharp angular turns and starts to spin into a vortex. This results in a reduction in the efficiency of the air stream to entrain and convey debris. This relative inefficiency can be overcome by providing greater air flow through the system, but this requires larger fans, motors, etc.; each of which add to the cost, power requirements, and/or weight of the system.
Another drawback with the aforementioned recirculating air system occurs at the head. Since there is high velocity turbulent air flow in the head, steps must be taken to prevent air from escaping the head while letting debris enter. This is typically achieved with front and rear skirts made from elastomeric materials. The skirting used, however, has limitations. One limitation, for example, is that a relatively pliable front skirt that is able to be deflected by light debris as it passes thereover and is not able to resist the force of air as it is drawn into the pick-up chamber. This results in the skirt being lifted away from the ground and toward the pick-up chamber creating a situation in which clouds of dust may get ejected from the head. This dusting may be reduced by providing a second skirt in front of the first skirt. However, use of such a second skirt has its drawbacks. Some of the debris which is captured between the skirts escapes at the ends, particularly when the air sweeper is cornering, to form trails. Conversely, another limitation is that a relatively stiff front skirt (one that is able to resist the force of air as it is drawn into the pick-up chamber) will not deflect when it encounters light debris. As a result, the skirt plows the lighter material in front of the head. This debris may accumulate between the skirting where it reduces overall efficiency and facilitates dusting and trailing. Yet another drawback occurs at the end wall of the pick-up chamber as it travels over an uneven surface. In operation, a localized high pressure zone is created at the end wall of the chamber. This does not present too much of a problem with relatively smooth surfaces. However, when the end wall of a pick-upchamber passes over a depression such as a pot hole, some of the air and entrained debris blows out of the chamber in yet another dust cloud.
Once debris has been entrained and transported to a suitable receptacle, the debris is usually separated from the air stream. There are several methods used to separate the debris from the air stream. One method mixes water with the dirty air stream. With this system, screens are used to separate larger debris from the mixture leaving the heavy debris to settle out of the water in a holding tank. The water is then recycled through the system. This method has its drawbacks. The water adds excess weight to the hopper and must be periodically cleaned. An additional concern is that of leakage and degradation. The hopper or bin may initially be water tight, but it may develop leaks over time. In other systems, small quantities of water are injected into the air stream to help separate dust from the air stream. This presents a problem, however, because when water is mixed with small or fine particulate matter, mud is formed. This mud clogs filters and reduces the efficiency of the air sweeper. The filters must, therefore, be periodically inspected and serviced to ensure that the air sweeper is operating within normal parameters.
Another method of separation uses the centrifugal force of debris to separate it from a cyclonic air stream. This is not without its drawbacks. One drawback is that the debris extracted from the air stream is often allowed to settle out in a main hopper. There, the debris is subject to internal air currents and may become re-entrained as the air stream swirls about the hopper. Alternatively, the extracted debris is collected in a secondary hopper internal to the main hopper. This alleviates some of the problems of re-entraining, however, the secondary hoppers are usually an afterthought. Additionally, the secondary hopper is usually provided with its own cover. Often, the secondary hoppers are not sealed and are loosely hinged. This allows dust contained therein to leak into the main hopper. Moreover, when emptying the hoppers, the secondary hopper is emptied into the main hopper as the main hopper is being dumped. This precludes continued separation of the differently sized debris and may complicate disposal.
There is a need for an air sweeper which may be adjustably configured depending upon the size and type of debris to be removed and collected from a surface. There is a need for an air sweeper with a collection chamber which is configured to suspendingly contain and transport debris in a predetermined pathway as the debris travels therealong. There is also a need for an air sweeper in which debris is separated according to size and weight, and collected in separate containers which may be accessible for emptying through a common access panel. And there is a need for an air sweeper which is able to remove and collect fine particulate matter from a surface without the assistance of liquids.
An air sweeper having a head assembly, a debris conveyer and a debris receptacle. The head assembly includes a first or main front skirt and a second front skirt which extend along the longitudinal extent of the head assembly in a generally parallel relation. The main front skirt is selectively positionable between different operational modes which enable the head assembly to collect debris of different or varying densities and sizes. In the first mode of operation, where relatively heavy debris is being collected, the main front skirt edge is in substantial contact with a surface to be cleaned as it is being drawn therealong. And, in a second mode of operation where relatively light debris is being collected, the main front skirt edge is shifted away from a surface to be cleaned as it is being drawn therealong to allow passage of the light debris thereby.
In both modes of operation, as the front skirting of the head assembly moves past debris the debris becomes entrained within a vortex formed by a sheet or curtain of pressurized air which circulates about a streamlined, curvilinear interior surface of the main chamber of the head assembly. Preferably, the streamlined interior surface of the main chamber is substantially ovate or circular in cross section along its longitudinal extent.
The interior components (ie., the main chamber, the first and second front skirts and the nozzle which produces the sheet or curtain of pressurized air) of the head assembly are skewed with respect to the direction of travel. This allows the vortex to direct debris towards an output portion or end of the main chamber. Upon reaching the output portion of the main chamber, the entrained debris exits the main chamber in a direction generally tangential to the vortex and directly into a debris conveyer which transports the debris into a debris receptacle. Generally, the output portion is contiguous with and substantially tangent to a predetermined circumferential surface of the main chamber. Preferably, the predetermined surface is a portion of or a portion adjacent to the upper edge of the main front skirt. The debris conveyor includes a low pressure conduit which operatively connects the output portion of the head assembly to the debris receptacle. Initially, the low pressure conduit discharges the entrained debris into a first hopper or bin. As the entrained debris enters the first hopper, the heavier material whose settling velocity exceeds the air velocity settles to the bottom of the hopper and the lighter, entrained material whose settling velocity is less than the air velocity is directed through a first filter element and into a second hopper or bin. The first filter element separates light debris such as paper and leaves from the air flow before it enters into the second hopper. As the air flow enters the second hopper, it is drawn into and through centrifugal separator which removes and deposits entrained light particulate matter in the second hopper. After emerging from the separator, the separator exhaust air stream enters an air handling device (typically a motorized fan surrounded by a shroud) where it is pressurized and directed to the input portion of the head assembly through a high pressure conduit. A portion of this high pressure air flow is directed via a bypass conduit towards a third hopper or bin in the debris receptacle where it is passed through a second filter element to remove fine particulate matter before it is exhausted.
The hoppers of the debris receptacle have discharge openings that are adjacent to each other and oriented so that they may be emptied at the same time by opening a common access panel and pivoting the debris receptacle about a hinge.
The main chamber of the head assembly includes an input portion and an output portion. The input portion or end of the head assembly includes one or more interior vanes to direct the pressurized air stream of the debris conveyer towards a manifold which is in communication with a nozzle. The input portion may also include a vane to direct air towards an optional bypass conduit operatively connected to the third hopper of the debris receptacle. The output end includes a barrier or inner wall which is configured to intercept entrained debris before it reaches the side at the end of the main chamber, thus minimizing trailing and dusting. As entrained debris encounters the barrier it deadheads and forms a localized high pressure zone, with the majority of the entrained debris being directed towards the output portion of the head assembly and into the debris receptacle. Fine debris which finds its way past the barrier enters a recovery chamber formed by the barrier and the side of the main chamber. The recovery chamber has a relatively lower pressure than the main chamber which allows fine particulate matter to be collected and removed to further reduce the chances of trailing or dusting. The baffle includes a stop surface which prevents the front skirt from being drawn into the output end of the head assembly when the air sweeping assembly is in the second mode of operation. Note that once the front skirt is shifted into the second mode of operation it tends to remain there due to the force of air flow being drawn into the main chamber.
The main front skirt is operatively connected to an actuator for movement between the first and second modes of operation. The actuator may be directly or indirectly connected to the front skirt so that the front skirt may be shifted away from a surface to be cleaned. The head assembly also includes side skirts which are positioned adjacent the sides of the head assembly and between the first and second front skirts. The side skirt located at the input portion of the head assembly facilitates the formation of a low pressure zone by impeding air movement directed thereagainst. This allows entrained debris which gets blown past the main front skirt to be directed back into the main chamber. The side skirt located at the output portion operates differently. Because the main front skirt has limited motion at the output portion of the head assembly, debris tends to accumulate. The side skirt located at the output portion of the head assembly directs this debris accumulation towards the center of the head assembly where it may be more readily collected.
The head assembly also includes a first rear or main skirt and a second rear skirt which also extend along the longitudinal extent of the head assembly in a generally parallel relation. The first and second rear skirts operate in a conventional manner. In order to minimize trailing and dusting, a scavenger strip is provided near the output end of the head assembly to direct fine particulate matter from a low pressure area bounded by the main rear skirt to the discharge area created at the nozzle.
Accordingly, it is an object of the present invention to provide an air sweeping system which effectively and efficiently collects and removes debris from a surface.
It is another object of the present invention to minimize debris plowing by a head assembly of an air sweeper as it moves along a surface.
Yet another object of the present invention is to increase the effectiveness of the chamber of a head assembly in transporting debris from an inlet end to an outlet end.
A feature of the present invention is the provision of a front skirt which may be selectively positioned to accommodate different types of debris.
Another feature of the present invention is that the main chamber of the head assembly is configured to foster the formation of a vortex along its longitudinal extent.
Yet another feature of the present invention is that the debris receptacle includes a plurality of hoppers which may be emptied at the same time.
An advantage of the present invention is that it does not require the use of liquids to suppress dust.
Another advantage is that filter plugging by light debris is reduced.
Yet another advantage of the present invention is that collection and dumping of debris is simplified.
These and further objects, features and advantages of the present invention will become clearer in light of the following detailed description of preferred embodiments in connection with the drawings.